act_simple.c

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/*
 * net/sched/simp.c Simple example of an action
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 * Authors: Jamal Hadi Salim (2005-8)
 *
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>

#define TCA_ACT_SIMP 22

#include <linux/tc_act/tc_defact.h>
#include <net/tc_act/tc_defact.h>

#define SIMP_TAB_MASK     7
static struct tcf_common *tcf_simp_ht[SIMP_TAB_MASK + 1];
static u32 simp_idx_gen;
static DEFINE_RWLOCK(simp_lock);

static struct tcf_hashinfo simp_hash_info = {
    .htab   =   tcf_simp_ht,
    .hmask  =   SIMP_TAB_MASK,
    .lock   =   &simp_lock,
};

#define SIMP_MAX_DATA   32
static int tcf_simp(struct sk_buff *skb, const struct tc_action *a,
            struct tcf_result *res)
{
    struct tcf_defact *d = a->priv;

    spin_lock(&d->tcf_lock);
    d->tcf_tm.lastuse = jiffies;
    bstats_update(&d->tcf_bstats, skb);

    /* print policy string followed by _ then packet count
     * Example if this was the 3rd packet and the string was "hello"
     * then it would look like "hello_3" (without quotes)
     */
    pr_info("simple: %s_%d\n",
           (char *)d->tcfd_defdata, d->tcf_bstats.packets);
    spin_unlock(&d->tcf_lock);
    return d->tcf_action;
}

static int tcf_simp_release(struct tcf_defact *d, int bind)
{
    int ret = 0;
    if (d) {
        if (bind)
            d->tcf_bindcnt--;
        d->tcf_refcnt--;
        if (d->tcf_bindcnt <= 0 && d->tcf_refcnt <= 0) {
            kfree(d->tcfd_defdata);
            tcf_hash_destroy(&d->common, &simp_hash_info);
            ret = 1;
        }
    }
    return ret;
}

static int alloc_defdata(struct tcf_defact *d, char *defdata)
{
    d->tcfd_defdata = kzalloc(SIMP_MAX_DATA, GFP_KERNEL);
    if (unlikely(!d->tcfd_defdata))
        return -ENOMEM;
    strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
    return 0;
}

static void reset_policy(struct tcf_defact *d, char *defdata,
             struct tc_defact *p)
{
    spin_lock_bh(&d->tcf_lock);
    d->tcf_action = p->action;
    memset(d->tcfd_defdata, 0, SIMP_MAX_DATA);
    strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
    spin_unlock_bh(&d->tcf_lock);
}

static const struct nla_policy simple_policy[TCA_DEF_MAX + 1] = {
    [TCA_DEF_PARMS] = { .len = sizeof(struct tc_defact) },
    [TCA_DEF_DATA]  = { .type = NLA_STRING, .len = SIMP_MAX_DATA },
};

static int tcf_simp_init(struct nlattr *nla, struct nlattr *est,
             struct tc_action *a, int ovr, int bind)
{
    struct nlattr *tb[TCA_DEF_MAX + 1];
    struct tc_defact *parm;
    struct tcf_defact *d;
    struct tcf_common *pc;
    char *defdata;
    int ret = 0, err;

    if (nla == NULL)
        return -EINVAL;

    err = nla_parse_nested(tb, TCA_DEF_MAX, nla, simple_policy);
    if (err < 0)
        return err;

    if (tb[TCA_DEF_PARMS] == NULL)
        return -EINVAL;

    if (tb[TCA_DEF_DATA] == NULL)
        return -EINVAL;

    parm = nla_data(tb[TCA_DEF_PARMS]);
    defdata = nla_data(tb[TCA_DEF_DATA]);

    pc = tcf_hash_check(parm->index, a, bind, &simp_hash_info);
    if (!pc) {
        pc = tcf_hash_create(parm->index, est, a, sizeof(*d), bind,
                     &simp_idx_gen, &simp_hash_info);
        if (IS_ERR(pc))
            return PTR_ERR(pc);

        d = to_defact(pc);
        ret = alloc_defdata(d, defdata);
        if (ret < 0) {
            if (est)
                gen_kill_estimator(&pc->tcfc_bstats,
                           &pc->tcfc_rate_est);
            kfree_rcu(pc, tcfc_rcu);
            return ret;
        }
        d->tcf_action = parm->action;
        ret = ACT_P_CREATED;
    } else {
        d = to_defact(pc);
        if (!ovr) {
            tcf_simp_release(d, bind);
            return -EEXIST;
        }
        reset_policy(d, defdata, parm);
    }

    if (ret == ACT_P_CREATED)
        tcf_hash_insert(pc, &simp_hash_info);
    return ret;
}

static int tcf_simp_cleanup(struct tc_action *a, int bind)
{
    struct tcf_defact *d = a->priv;

    if (d)
        return tcf_simp_release(d, bind);
    return 0;
}

static int tcf_simp_dump(struct sk_buff *skb, struct tc_action *a,
             int bind, int ref)
{
    unsigned char *b = skb_tail_pointer(skb);
    struct tcf_defact *d = a->priv;
    struct tc_defact opt = {
        .index   = d->tcf_index,
        .refcnt  = d->tcf_refcnt - ref,
        .bindcnt = d->tcf_bindcnt - bind,
        .action  = d->tcf_action,
    };
    struct tcf_t t;

    if (nla_put(skb, TCA_DEF_PARMS, sizeof(opt), &opt) ||
        nla_put_string(skb, TCA_DEF_DATA, d->tcfd_defdata))
        goto nla_put_failure;
    t.install = jiffies_to_clock_t(jiffies - d->tcf_tm.install);
    t.lastuse = jiffies_to_clock_t(jiffies - d->tcf_tm.lastuse);
    t.expires = jiffies_to_clock_t(d->tcf_tm.expires);
    if (nla_put(skb, TCA_DEF_TM, sizeof(t), &t))
        goto nla_put_failure;
    return skb->len;

nla_put_failure:
    nlmsg_trim(skb, b);
    return -1;
}

static struct tc_action_ops act_simp_ops = {
    .kind       =   "simple",
    .hinfo      =   &simp_hash_info,
    .type       =   TCA_ACT_SIMP,
    .capab      =   TCA_CAP_NONE,
    .owner      =   THIS_MODULE,
    .act        =   tcf_simp,
    .dump       =   tcf_simp_dump,
    .cleanup    =   tcf_simp_cleanup,
    .init       =   tcf_simp_init,
    .walk       =   tcf_generic_walker,
};

MODULE_AUTHOR("Jamal Hadi Salim(2005)");
MODULE_DESCRIPTION("Simple example action");
MODULE_LICENSE("GPL");

static int __init simp_init_module(void)
{
    int ret = tcf_register_action(&act_simp_ops);
    if (!ret)
        pr_info("Simple TC action Loaded\n");
    return ret;
}

static void __exit simp_cleanup_module(void)
{
    tcf_unregister_action(&act_simp_ops);
}

module_init(simp_init_module);
module_exit(simp_cleanup_module);